1. Field of the Invention
The invention relates to a method and a processing installation for devolatilizing polymer melts.
2. Background Art
Devolatilizing of polymer melts for improving the polymer quality is a common procedure in the industrial production of plastic materials. In this process, volatile components such as monomers, oligomers, additives required for polymerization as well as undesirable by-products impairing the quality of the polymer are devolatilized. Typical additives are for example solvents or suspending agents. The process of devolatilization allows in particular the optical and mechanical properties to be improved.
US 2006/0245294 A1 discloses a processing installation and a method for devolatilizing bimodal polyolefins. In the processing installation, two twin-shaft extruders which rotate in the same direction are arranged one behind the other, with the second extruder, seen in the direction of conveyance, having a devolatilization zone for devolatilizing the polyolefins to be processed. The drawback of this processing installation is that the devolatilization performance, in other words the amount of the devolatilized proportion of undesirable volatile components, is low.
U.S. Pat. No. 6,024,479 discloses a method and an extrusion installation for processing materials which emit large amounts of gas. The extrusion installation comprises a main extruder and two ancillary extruders opening laterally into the main extruder so that the gas flow produced in an evaporation zone of the main extruder is divided into at least three partial flows which are then discharged from the extruders. The drawback is that the material throughput in this extrusion installation is low compared to the necessary technical effort.